text: /*
   *	watchdog_dev.c
   *
   *	(c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
   *						All Rights Reserved.
   *
   *	(c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
   *
   *
   *	This source code is part of the generic code that can be used
   *	by all the watchdog timer drivers.
   *
   *	This part of the generic code takes care of the following
   *	misc device: /dev/watchdog.
   *
   *	Based on source code of the following authors:
   *	  Matt Domsch <Matt_Domsch@dell.com>,
   *	  Rob Radez <rob@osinvestor.com>,
   *	  Rusty Lynch <rusty@linux.co.intel.com>
   *	  Satyam Sharma <satyam@infradead.org>
   *	  Randy Dunlap <randy.dunlap@oracle.com>
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License
   *	as published by the Free Software Foundation; either version
   *	2 of the License, or (at your option) any later version.
   *
   *	Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
   *	admit liability nor provide warranty for any of this software.
   *	This material is provided "AS-IS" and at no charge.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/cdev.h>		/* For character device */
  #include <linux/errno.h>	/* For the -ENODEV/... values */
  #include <linux/fs.h>		/* For file operations */
  #include <linux/init.h>		/* For __init/__exit/... */
  #include <linux/jiffies.h>	/* For timeout functions */
  #include <linux/kernel.h>	/* For printk/panic/... */
  #include <linux/kref.h>		/* For data references */
  #include <linux/miscdevice.h>	/* For handling misc devices */
  #include <linux/module.h>	/* For module stuff/... */
  #include <linux/mutex.h>	/* For mutexes */
  #include <linux/slab.h>		/* For memory functions */
  #include <linux/types.h>	/* For standard types (like size_t) */
  #include <linux/watchdog.h>	/* For watchdog specific items */
  #include <linux/workqueue.h>	/* For workqueue */
  #include <linux/uaccess.h>	/* For copy_to_user/put_user/... */
  
  #include "watchdog_core.h"
  
  /*
   * struct watchdog_core_data - watchdog core internal data
   * @kref:	Reference count.
   * @cdev:	The watchdog's Character device.
   * @wdd:	Pointer to watchdog device.
   * @lock:	Lock for watchdog core.
   * @status:	Watchdog core internal status bits.
   */
  struct watchdog_core_data {
  	struct kref kref;
  	struct cdev cdev;
  	struct watchdog_device *wdd;
  	struct mutex lock;
  	unsigned long last_keepalive;
  	unsigned long last_hw_keepalive;
  	struct delayed_work work;
  	unsigned long status;		/* Internal status bits */
  #define _WDOG_DEV_OPEN		0	/* Opened ? */
  #define _WDOG_ALLOW_RELEASE	1	/* Did we receive the magic char ? */
  };
  
  /* the dev_t structure to store the dynamically allocated watchdog devices */
  static dev_t watchdog_devt;
  /* Reference to watchdog device behind /dev/watchdog */
  static struct watchdog_core_data *old_wd_data;
  
  static struct workqueue_struct *watchdog_wq;
  
  static inline bool watchdog_need_worker(struct watchdog_device *wdd)
  {
  	/* All variables in milli-seconds */
  	unsigned int hm = wdd->max_hw_heartbeat_ms;
  	unsigned int t = wdd->timeout * 1000;
  
  	/*
  	 * A worker to generate heartbeat requests is needed if all of the
  	 * following conditions are true.
  	 * - Userspace activated the watchdog.
  	 * - The driver provided a value for the maximum hardware timeout, and
  	 *   thus is aware that the framework supports generating heartbeat
  	 *   requests.
  	 * - Userspace requests a longer timeout than the hardware can handle.
  	 */
  	return hm && ((watchdog_active(wdd) && t > hm) ||
  		      (t && !watchdog_active(wdd) && watchdog_hw_running(wdd)));
  }
  
  static long watchdog_next_keepalive(struct watchdog_device *wdd)
  {
  	struct watchdog_core_data *wd_data = wdd->wd_data;
  	unsigned int timeout_ms = wdd->timeout * 1000;
  	unsigned long keepalive_interval;
  	unsigned long last_heartbeat;
  	unsigned long virt_timeout;
  	unsigned int hw_heartbeat_ms;
  
  	virt_timeout = wd_data->last_keepalive + msecs_to_jiffies(timeout_ms);
  	hw_heartbeat_ms = min(timeout_ms, wdd->max_hw_heartbeat_ms);
  	keepalive_interval = msecs_to_jiffies(hw_heartbeat_ms / 2);
  
  	if (!watchdog_active(wdd))
  		return keepalive_interval;
  
  	/*
  	 * To ensure that the watchdog times out wdd->timeout seconds
  	 * after the most recent ping from userspace, the last
  	 * worker ping has to come in hw_heartbeat_ms before this timeout.
  	 */
  	last_heartbeat = virt_timeout - msecs_to_jiffies(hw_heartbeat_ms);
  	return min_t(long, last_heartbeat - jiffies, keepalive_interval);
  }
  
  static inline void watchdog_update_worker(struct watchdog_device *wdd)
  {
  	struct watchdog_core_data *wd_data = wdd->wd_data;
  
  	if (watchdog_need_worker(wdd)) {
  		long t = watchdog_next_keepalive(wdd);
  
  		if (t > 0)
  			mod_delayed_work(watchdog_wq, &wd_data->work, t);
  	} else {
  		cancel_delayed_work(&wd_data->work);
  	}
  }
  
  static int __watchdog_ping(struct watchdog_device *wdd)
  {
  	struct watchdog_core_data *wd_data = wdd->wd_data;
  	unsigned long earliest_keepalive = wd_data->last_hw_keepalive +
  				msecs_to_jiffies(wdd->min_hw_heartbeat_ms);
  	int err;
  
  	if (time_is_after_jiffies(earliest_keepalive)) {
  		mod_delayed_work(watchdog_wq, &wd_data->work,
  				 earliest_keepalive - jiffies);
  		return 0;
  	}
  
  	wd_data->last_hw_keepalive = jiffies;
  
  	if (wdd->ops->ping)
  		err = wdd->ops->ping(wdd);  /* ping the watchdog */
  	else
  		err = wdd->ops->start(wdd); /* restart watchdog */
  
  	watchdog_update_worker(wdd);
  
  	return err;
  }
  
  /*
   *	watchdog_ping: ping the watchdog.
   *	@wdd: the watchdog device to ping
   *
   *	The caller must hold wd_data->lock.
   *
   *	If the watchdog has no own ping operation then it needs to be
   *	restarted via the start operation. This wrapper function does
   *	exactly that.
   *	We only ping when the watchdog device is running.
   */
  
  static int watchdog_ping(struct watchdog_device *wdd)
  {
  	struct watchdog_core_data *wd_data = wdd->wd_data;
  
  	if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
  		return 0;
  
  	wd_data->last_keepalive = jiffies;
  	return __watchdog_ping(wdd);
  }
  
  static void watchdog_ping_work(struct work_struct *work)
  {
  	struct watchdog_core_data *wd_data;
  	struct watchdog_device *wdd;
  
  	wd_data = container_of(to_delayed_work(work), struct watchdog_core_data,
  			       work);
  
  	mutex_lock(&wd_data->lock);
  	wdd = wd_data->wdd;
  	if (wdd && (watchdog_active(wdd) || watchdog_hw_running(wdd)))
  		__watchdog_ping(wdd);
  	mutex_unlock(&wd_data->lock);
  }
  
  /*
   *	watchdog_start: wrapper to start the watchdog.
   *	@wdd: the watchdog device to start
   *
   *	The caller must hold wd_data->lock.
   *
   *	Start the watchdog if it is not active and mark it active.
   *	This function returns zero on success or a negative errno code for
   *	failure.
   */
  
  static int watchdog_start(struct watchdog_device *wdd)
  {
  	struct watchdog_core_data *wd_data = wdd->wd_data;
  	unsigned long started_at;
  	int err;
  
  	if (watchdog_active(wdd))
  		return 0;
  
  	started_at = jiffies;
  	if (watchdog_hw_running(wdd) && wdd->ops->ping)
  		err = wdd->ops->ping(wdd);
  	else
  		err = wdd->ops->start(wdd);
  	if (err == 0) {
  		set_bit(WDOG_ACTIVE, &wdd->status);
  		wd_data->last_keepalive = started_at;
  		watchdog_update_worker(wdd);
  	}
  
  	return err;
  }
  
  /*
   *	watchdog_stop: wrapper to stop the watchdog.
   *	@wdd: the watchdog device to stop
   *
   *	The caller must hold wd_data->lock.
   *
   *	Stop the watchdog if it is still active and unmark it active.
   *	This function returns zero on success or a negative errno code for
   *	failure.
   *	If the 'nowayout' feature was set, the watchdog cannot be stopped.
   */
  
  static int watchdog_stop(struct watchdog_device *wdd)
  {
  	int err = 0;
  
  	if (!watchdog_active(wdd))
  		return 0;
  
  	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
  		pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
  			wdd->id);
  		return -EBUSY;
  	}
  
  	if (wdd->ops->stop)
  		err = wdd->ops->stop(wdd);
  	else
  		set_bit(WDOG_HW_RUNNING, &wdd->status);
  
  	if (err == 0) {
  		clear_bit(WDOG_ACTIVE, &wdd->status);
  		watchdog_update_worker(wdd);
  	}
  
  	return err;
  }
  
  /*
   *	watchdog_get_status: wrapper to get the watchdog status
   *	@wdd: the watchdog device to get the status from
   *
   *	The caller must hold wd_data->lock.
   *
   *	Get the watchdog's status flags.
   */
  
  static unsigned int watchdog_get_status(struct watchdog_device *wdd)
  {
  	if (!wdd->ops->status)
  		return 0;
  
  	return wdd->ops->status(wdd);
  }
  
  /*
   *	watchdog_set_timeout: set the watchdog timer timeout
   *	@wdd: the watchdog device to set the timeout for
   *	@timeout: timeout to set in seconds
   *
   *	The caller must hold wd_data->lock.
   */
  
  static int watchdog_set_timeout(struct watchdog_device *wdd,
  							unsigned int timeout)
  {
  	int err = 0;
  
  	if (!(wdd->info->options & WDIOF_SETTIMEOUT))
  		return -EOPNOTSUPP;
  
  	if (watchdog_timeout_invalid(wdd, timeout))
  		return -EINVAL;
  
  	if (wdd->ops->set_timeout)
  		err = wdd->ops->set_timeout(wdd, timeout);
  	else
  		wdd->timeout = timeout;
  
  	watchdog_update_worker(wdd);
  
  	return err;
  }
  
  /*
   *	watchdog_get_timeleft: wrapper to get the time left before a reboot
   *	@wdd: the watchdog device to get the remaining time from
   *	@timeleft: the time that's left
   *
   *	The caller must hold wd_data->lock.
   *
   *	Get the time before a watchdog will reboot (if not pinged).
   */
  
  static int watchdog_get_timeleft(struct watchdog_device *wdd,
  							unsigned int *timeleft)
  {
  	*timeleft = 0;
  
  	if (!wdd->ops->get_timeleft)
  		return -EOPNOTSUPP;
  
  	*timeleft = wdd->ops->get_timeleft(wdd);
  
  	return 0;
  }
  
  #ifdef CONFIG_WATCHDOG_SYSFS
  static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
  				char *buf)
  {
  	struct watchdog_device *wdd = dev_get_drvdata(dev);
  
  	return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
  }
  static DEVICE_ATTR_RO(nowayout);
  
  static ssize_t status_show(struct device *dev, struct device_attribute *attr,
  				char *buf)
  {
  	struct watchdog_device *wdd = dev_get_drvdata(dev);
  	struct watchdog_core_data *wd_data = wdd->wd_data;
  	unsigned int status;
  
  	mutex_lock(&wd_data->lock);
  	status = watchdog_get_status(wdd);
  	mutex_unlock(&wd_data->lock);
  
  	return sprintf(buf, "%u\n", status);
  }
  static DEVICE_ATTR_RO(status);
  
  static ssize_t bootstatus_show(struct device *dev,
  				struct device_attribute *attr, char *buf)
  {
  	struct watchdog_device *wdd = dev_get_drvdata(dev);
  
  	return sprintf(buf, "%u\n", wdd->bootstatus);
  }
  static DEVICE_ATTR_RO(bootstatus);
  
  static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
  				char *buf)
  {
  	struct watchdog_device *wdd = dev_get_drvdata(dev);
  	struct watchdog_core_data *wd_data = wdd->wd_data;
  	ssize_t status;
  	unsigned int val;
  
  	mutex_lock(&wd_data->lock);
  	status = watchdog_get_timeleft(wdd, &val);
  	mutex_unlock(&wd_data->lock);
  	if (!status)
  		status = sprintf(buf, "%u\n", val);
  
  	return status;
  }
  static DEVICE_ATTR_RO(timeleft);
  
  static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
  				char *buf)
  {
  	struct watchdog_device *wdd = dev_get_drvdata(dev);
  
  	return sprintf(buf, "%u\n", wdd->timeout);
  }
  static DEVICE_ATTR_RO(timeout);
  
  static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
  				char *buf)
  {
  	struct watchdog_device *wdd = dev_get_drvdata(dev);
  
  	return sprintf(buf, "%s\n", wdd->info->identity);
  }
  static DEVICE_ATTR_RO(identity);
  
  static ssize_t state_show(struct device *dev, struct device_attribute *attr,
  				char *buf)
  {
  	struct watchdog_device *wdd = dev_get_drvdata(dev);
  
  	if (watchdog_active(wdd))
  		return sprintf(buf, "active\n");
  
  	return sprintf(buf, "inactive\n");
  }
  static DEVICE_ATTR_RO(state);
  
  static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
  				int n)
  {
  	struct device *dev = container_of(kobj, struct device, kobj);
  	struct watchdog_device *wdd = dev_get_drvdata(dev);
  	umode_t mode = attr->mode;
  
  	if (attr == &dev_attr_status.attr && !wdd->ops->status)
  		mode = 0;
  	else if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
  		mode = 0;
  
  	return mode;
  }
  static struct attribute *wdt_attrs[] = {
  	&dev_attr_state.attr,
  	&dev_attr_identity.attr,
  	&dev_attr_timeout.attr,
  	&dev_attr_timeleft.attr,
  	&dev_attr_bootstatus.attr,
  	&dev_attr_status.attr,
  	&dev_attr_nowayout.attr,
  	NULL,
  };
  
  static const struct attribute_group wdt_group = {
  	.attrs = wdt_attrs,
  	.is_visible = wdt_is_visible,
  };
  __ATTRIBUTE_GROUPS(wdt);
  #else
  #define wdt_groups	NULL
  #endif
  
  /*
   *	watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
   *	@wdd: the watchdog device to do the ioctl on
   *	@cmd: watchdog command
   *	@arg: argument pointer
   *
   *	The caller must hold wd_data->lock.
   */
  
  static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
  							unsigned long arg)
  {
  	if (!wdd->ops->ioctl)
  		return -ENOIOCTLCMD;
  
  	return wdd->ops->ioctl(wdd, cmd, arg);
  }
  
  /*
   *	watchdog_write: writes to the watchdog.
   *	@file: file from VFS
   *	@data: user address of data
   *	@len: length of data
   *	@ppos: pointer to the file offset
   *
   *	A write to a watchdog device is defined as a keepalive ping.
   *	Writing the magic 'V' sequence allows the next close to turn
   *	off the watchdog (if 'nowayout' is not set).
   */
  
  static ssize_t watchdog_write(struct file *file, const char __user *data,
  						size_t len, loff_t *ppos)
  {
  	struct watchdog_core_data *wd_data = file->private_data;
  	struct watchdog_device *wdd;
  	int err;
  	size_t i;
  	char c;
  
  	if (len == 0)
  		return 0;
  
  	/*
  	 * Note: just in case someone wrote the magic character
  	 * five months ago...
  	 */
  	clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
  
  	/* scan to see whether or not we got the magic character */
  	for (i = 0; i != len; i++) {
  		if (get_user(c, data + i))
  			return -EFAULT;
  		if (c == 'V')
  			set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
  	}
  
  	/* someone wrote to us, so we send the watchdog a keepalive ping */
  
  	err = -ENODEV;
  	mutex_lock(&wd_data->lock);
  	wdd = wd_data->wdd;
  	if (wdd)
  		err = watchdog_ping(wdd);
  	mutex_unlock(&wd_data->lock);
  
  	if (err < 0)
  		return err;
  
  	return len;
  }
  
  /*
   *	watchdog_ioctl: handle the different ioctl's for the watchdog device.
   *	@file: file handle to the device
   *	@cmd: watchdog command
   *	@arg: argument pointer
   *
   *	The watchdog API defines a common set of functions for all watchdogs
   *	according to their available features.
   */
  
  static long watchdog_ioctl(struct file *file, unsigned int cmd,
  							unsigned long arg)
  {
  	struct watchdog_core_data *wd_data = file->private_data;
  	void __user *argp = (void __user *)arg;
  	struct watchdog_device *wdd;
  	int __user *p = argp;
  	unsigned int val;
  	int err;
  
  	mutex_lock(&wd_data->lock);
  
  	wdd = wd_data->wdd;
  	if (!wdd) {
  		err = -ENODEV;
  		goto out_ioctl;
  	}
  
  	err = watchdog_ioctl_op(wdd, cmd, arg);
  	if (err != -ENOIOCTLCMD)
  		goto out_ioctl;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		err = copy_to_user(argp, wdd->info,
  			sizeof(struct watchdog_info)) ? -EFAULT : 0;
  		break;
  	case WDIOC_GETSTATUS:
  		val = watchdog_get_status(wdd);
  		err = put_user(val, p);
  		break;
  	case WDIOC_GETBOOTSTATUS:
  		err = put_user(wdd->bootstatus, p);
  		break;
  	case WDIOC_SETOPTIONS:
  		if (get_user(val, p)) {
  			err = -EFAULT;
  			break;
  		}
  		if (val & WDIOS_DISABLECARD) {
  			err = watchdog_stop(wdd);
  			if (err < 0)
  				break;
  		}
  		if (val & WDIOS_ENABLECARD)
  			err = watchdog_start(wdd);
  		break;
  	case WDIOC_KEEPALIVE:
  		if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
  			err = -EOPNOTSUPP;
  			break;
  		}
  		err = watchdog_ping(wdd);
  		break;
  	case WDIOC_SETTIMEOUT:
  		if (get_user(val, p)) {
  			err = -EFAULT;
  			break;
  		}
  		err = watchdog_set_timeout(wdd, val);
  		if (err < 0)
  			break;
  		/* If the watchdog is active then we send a keepalive ping
  		 * to make sure that the watchdog keep's running (and if
  		 * possible that it takes the new timeout) */
  		err = watchdog_ping(wdd);
  		if (err < 0)
  			break;
  		/* Fall */
  	case WDIOC_GETTIMEOUT:
  		/* timeout == 0 means that we don't know the timeout */
  		if (wdd->timeout == 0) {
  			err = -EOPNOTSUPP;
  			break;
  		}
  		err = put_user(wdd->timeout, p);
  		break;
  	case WDIOC_GETTIMELEFT:
  		err = watchdog_get_timeleft(wdd, &val);
  		if (err < 0)
  			break;
  		err = put_user(val, p);
  		break;
  	default:
  		err = -ENOTTY;
  		break;
  	}
  
  out_ioctl:
  	mutex_unlock(&wd_data->lock);
  	return err;
  }
  
  /*
   *	watchdog_open: open the /dev/watchdog* devices.
   *	@inode: inode of device
   *	@file: file handle to device
   *
   *	When the /dev/watchdog* device gets opened, we start the watchdog.
   *	Watch out: the /dev/watchdog device is single open, so we make sure
   *	it can only be opened once.
   */
  
  static int watchdog_open(struct inode *inode, struct file *file)
  {
  	struct watchdog_core_data *wd_data;
  	struct watchdog_device *wdd;
  	int err;
  
  	/* Get the corresponding watchdog device */
  	if (imajor(inode) == MISC_MAJOR)
  		wd_data = old_wd_data;
  	else
  		wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
  				       cdev);
  
  	/* the watchdog is single open! */
  	if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
  		return -EBUSY;
  
  	wdd = wd_data->wdd;
  
  	/*
  	 * If the /dev/watchdog device is open, we don't want the module
  	 * to be unloaded.
  	 */
  	if (!watchdog_hw_running(wdd) && !try_module_get(wdd->ops->owner)) {
  		err = -EBUSY;
  		goto out_clear;
  	}
  
  	err = watchdog_start(wdd);
  	if (err < 0)
  		goto out_mod;
  
  	file->private_data = wd_data;
  
  	if (!watchdog_hw_running(wdd))
  		kref_get(&wd_data->kref);
  
  	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
  	return nonseekable_open(inode, file);
  
  out_mod:
  	module_put(wd_data->wdd->ops->owner);
  out_clear:
  	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
  	return err;
  }
  
  static void watchdog_core_data_release(struct kref *kref)
  {
  	struct watchdog_core_data *wd_data;
  
  	wd_data = container_of(kref, struct watchdog_core_data, kref);
  
  	kfree(wd_data);
  }
  
  /*
   *	watchdog_release: release the watchdog device.
   *	@inode: inode of device
   *	@file: file handle to device
   *
   *	This is the code for when /dev/watchdog gets closed. We will only
   *	stop the watchdog when we have received the magic char (and nowayout
   *	was not set), else the watchdog will keep running.
   */
  
  static int watchdog_release(struct inode *inode, struct file *file)
  {
  	struct watchdog_core_data *wd_data = file->private_data;
  	struct watchdog_device *wdd;
  	int err = -EBUSY;
  	bool running;
  
  	mutex_lock(&wd_data->lock);
  
  	wdd = wd_data->wdd;
  	if (!wdd)
  		goto done;
  
  	/*
  	 * We only stop the watchdog if we received the magic character
  	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
  	 * watchdog_stop will fail.
  	 */
  	if (!test_bit(WDOG_ACTIVE, &wdd->status))
  		err = 0;
  	else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
  		 !(wdd->info->options & WDIOF_MAGICCLOSE))
  		err = watchdog_stop(wdd);
  
  	/* If the watchdog was not stopped, send a keepalive ping */
  	if (err < 0) {
  		pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
  		watchdog_ping(wdd);
  	}
  
  	watchdog_update_worker(wdd);
  
  	/* make sure that /dev/watchdog can be re-opened */
  	clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
  
  done:
  	running = wdd && watchdog_hw_running(wdd);
  	mutex_unlock(&wd_data->lock);
  	/*
  	 * Allow the owner module to be unloaded again unless the watchdog
  	 * is still running. If the watchdog is still running, it can not
  	 * be stopped, and its driver must not be unloaded.
  	 */
  	if (!running) {
  		module_put(wd_data->cdev.owner);
  		kref_put(&wd_data->kref, watchdog_core_data_release);
  	}
  	return 0;
  }
  
  static const struct file_operations watchdog_fops = {
  	.owner		= THIS_MODULE,
  	.write		= watchdog_write,
  	.unlocked_ioctl	= watchdog_ioctl,
  	.open		= watchdog_open,
  	.release	= watchdog_release,
  };
  
  static struct miscdevice watchdog_miscdev = {
  	.minor		= WATCHDOG_MINOR,
  	.name		= "watchdog",
  	.fops		= &watchdog_fops,
  };
  
  /*
   *	watchdog_cdev_register: register watchdog character device
   *	@wdd: watchdog device
   *	@devno: character device number
   *
   *	Register a watchdog character device including handling the legacy
   *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
   *	thus we set it up like that.
   */
  
  static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
  {
  	struct watchdog_core_data *wd_data;
  	int err;
  
  	wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
  	if (!wd_data)
  		return -ENOMEM;
  	kref_init(&wd_data->kref);
  	mutex_init(&wd_data->lock);
  
  	wd_data->wdd = wdd;
  	wdd->wd_data = wd_data;
  
  	if (!watchdog_wq)
  		return -ENODEV;
  
  	INIT_DELAYED_WORK(&wd_data->work, watchdog_ping_work);
  
  	if (wdd->id == 0) {
  		old_wd_data = wd_data;
  		watchdog_miscdev.parent = wdd->parent;
  		err = misc_register(&watchdog_miscdev);
  		if (err != 0) {
  			pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
  				wdd->info->identity, WATCHDOG_MINOR, err);
  			if (err == -EBUSY)
  				pr_err("%s: a legacy watchdog module is probably present.\n",
  					wdd->info->identity);
  			old_wd_data = NULL;
  			kfree(wd_data);
  			return err;
  		}
  	}
  
  	/* Fill in the data structures */
  	cdev_init(&wd_data->cdev, &watchdog_fops);
  	wd_data->cdev.owner = wdd->ops->owner;
  
  	/* Add the device */
  	err = cdev_add(&wd_data->cdev, devno, 1);
  	if (err) {
  		pr_err("watchdog%d unable to add device %d:%d\n",
  			wdd->id,  MAJOR(watchdog_devt), wdd->id);
  		if (wdd->id == 0) {
  			misc_deregister(&watchdog_miscdev);
  			old_wd_data = NULL;
  			kref_put(&wd_data->kref, watchdog_core_data_release);
  		}
  		return err;
  	}
  
  	/* Record time of most recent heartbeat as 'just before now'. */
  	wd_data->last_hw_keepalive = jiffies - 1;
  
  	/*
  	 * If the watchdog is running, prevent its driver from being unloaded,
  	 * and schedule an immediate ping.
  	 */
  	if (watchdog_hw_running(wdd)) {
  		__module_get(wdd->ops->owner);
  		kref_get(&wd_data->kref);
  		queue_delayed_work(watchdog_wq, &wd_data->work, 0);
  	}
  
  	return 0;
  }
  
  /*
   *	watchdog_cdev_unregister: unregister watchdog character device
   *	@watchdog: watchdog device
   *
   *	Unregister watchdog character device and if needed the legacy
   *	/dev/watchdog device.
   */
  
  static void watchdog_cdev_unregister(struct watchdog_device *wdd)
  {
  	struct watchdog_core_data *wd_data = wdd->wd_data;
  
  	cdev_del(&wd_data->cdev);
  	if (wdd->id == 0) {
  		misc_deregister(&watchdog_miscdev);
  		old_wd_data = NULL;
  	}
  
  	mutex_lock(&wd_data->lock);
  	wd_data->wdd = NULL;
  	wdd->wd_data = NULL;
  	mutex_unlock(&wd_data->lock);
  
  	cancel_delayed_work_sync(&wd_data->work);
  
  	kref_put(&wd_data->kref, watchdog_core_data_release);
  }
  
  static struct class watchdog_class = {
  	.name =		"watchdog",
  	.owner =	THIS_MODULE,
  	.dev_groups =	wdt_groups,
  };
  
  /*
   *	watchdog_dev_register: register a watchdog device
   *	@wdd: watchdog device
   *
   *	Register a watchdog device including handling the legacy
   *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
   *	thus we set it up like that.
   */
  
  int watchdog_dev_register(struct watchdog_device *wdd)
  {
  	struct device *dev;
  	dev_t devno;
  	int ret;
  
  	devno = MKDEV(MAJOR(watchdog_devt), wdd->id);
  
  	ret = watchdog_cdev_register(wdd, devno);
  	if (ret)
  		return ret;
  
  	dev = device_create_with_groups(&watchdog_class, wdd->parent,
  					devno, wdd, wdd->groups,
  					"watchdog%d", wdd->id);
  	if (IS_ERR(dev)) {
  		watchdog_cdev_unregister(wdd);
  		return PTR_ERR(dev);
  	}
  
  	return ret;
  }
  
  /*
   *	watchdog_dev_unregister: unregister a watchdog device
   *	@watchdog: watchdog device
   *
   *	Unregister watchdog device and if needed the legacy
   *	/dev/watchdog device.
   */
  
  void watchdog_dev_unregister(struct watchdog_device *wdd)
  {
  	device_destroy(&watchdog_class, wdd->wd_data->cdev.dev);
  	watchdog_cdev_unregister(wdd);
  }
  
  /*
   *	watchdog_dev_init: init dev part of watchdog core
   *
   *	Allocate a range of chardev nodes to use for watchdog devices
   */
  
  int __init watchdog_dev_init(void)
  {
  	int err;
  
  	watchdog_wq = alloc_workqueue("watchdogd",
  				      WQ_HIGHPRI | WQ_MEM_RECLAIM, 0);
  	if (!watchdog_wq) {
  		pr_err("Failed to create watchdog workqueue\n");
  		return -ENOMEM;
  	}
  
  	err = class_register(&watchdog_class);
  	if (err < 0) {
  		pr_err("couldn't register class\n");
  		return err;
  	}
  
  	err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
  	if (err < 0) {
  		pr_err("watchdog: unable to allocate char dev region\n");
  		class_unregister(&watchdog_class);
  		return err;
  	}
  
  	return 0;
  }
  
  /*
   *	watchdog_dev_exit: exit dev part of watchdog core
   *
   *	Release the range of chardev nodes used for watchdog devices
   */
  
  void __exit watchdog_dev_exit(void)
  {
  	unregister_chrdev_region(watchdog_devt, MAX_DOGS);
  	class_unregister(&watchdog_class);
  	destroy_workqueue(watchdog_wq);
  }
  